If an organisation you're trading with requires a vendor number, you will be able to view or add it when accepting the community invitation.

You can always add your vendor number in your organisation's settings:

1. Go to your organisation by clicking on the building icon, or your organisation's name in the top right of the menu
2. In the navigation on the left, click organisation settings > general settings > identifiers
3. Click on ADD NEW + next to  Community identifiers.
4. Under community, select the community you're adding the vendor number for
5. Under Identifier Type, select Vendor number
6. Under Identification value, enter your vendor number
7. Click ADD button.
   

Note: If you are using a vendor number as your 'mock' GLN please select GLN in step 4.